Salt-saturated supramolecular solvent microextraction for spectrophotometric determination of curcumin in food...

A salt-saturated supramolecular solvent-based liquid-liquid microextraction method coupled with UV-Vis spectrophotometry was developed for the sensitive determination of trace levels of curcumin in food samples. Supramolecular solvents formed from decanol and tetrahydrofuran were employed as the extraction phase, while a mixed salt system (NaCl, Mg(NO₃)₂·6H₂O, and KNO₃) was used to enhance extraction efficiency through a salting-out effect. Key experimental parameters influencing extraction performance, including pH, extraction solvent volumes, mixing time, and centrifugation conditions, were optimized using Box-Behnken design combined with response surface methodology. Under optimal conditions, the proposed method exhibited a linear response over the concentration range of 1.0 µg/L - 5.0 mg/L with a limit of detection of 0.23 µg/L. An enrichment factor of 131 was achieved within a total extraction time of 6 min. The method demonstrated good precision, with relative standard deviations below 3.7%. Compared with supramolecular solvent microextraction without salt saturation, the proposed approach provided an average signal enhancement of 32.7%. The method was successfully applied to the determination of curcumin in tomato, apple and fish samples, yielding recoveries between 98.0% and 99.7%. Owing to its simplicity, rapidity, low solvent consumption, and satisfactory analytical performance, the developed method represents a green and efficient alternative for routine spectrophotometric analysis of curcumin in food matrices.